Refrigerating apparatus



Feb. 6, 1940.

A. o. GROOMS 2,189,663

REFRIGERATING APPARATUS Filed Oct. 30, 1936 3 Sheets-Sheet 1 INVENTOR.

ATTORNEYS Feb. 6, 1940. A. 'o. GROOMS REFRIGERATING APPARATUS 5Shets-Sheet 2 Filed Oct. 30, 1936 INVENTOR.

gadwo/ ATTORNEYS Feb. 6, 1940; O GROOMS v 2,189,663

REFRIGERATING APPARATUS Filed Oct. 50, 1936 3 Sheets-Sheet 3 QQZWITO BYI 10 20 50 40 z 5 2,4 44 4W -24 INVENTOR.

TEMPERATURE "F ATTORNEYS Patented Feb. 6, 1940 UNITED STATES PATENTOFFICE REFRIGERATING APPARATUS poration of Delaware Application October30, 1936, Serial No. 108,377

12 Claims.

This invention relates to refrigerating apparatus and more particularlyto control means therefor.

Heretofore, low differential switches for refrigerating systems andtemperature controls mainly have had bimetal as the actuating element.Bimetal switches, because of their low contact pressures, can ordinarilycarry only a small amount of current at a low voltage. This necessitatesthe use of a relay in order to control heavier currents.

In refrigerating systems and other temperature controls, it is oftendesirable to have a more simple arrangement wherein the relay iseliminated and it is usually desired to employ a switch operated by gaspressure. Considerable difficulties are encountered in attempting tomake a low differential switch operated by gas pressure. In the firstplace, the metal bellows, which are ordinarily used in such switches,may in the present state of the art, operate only in a compressedcondition to avoid bellows failure. When operating under such conditionsthe natural spring of the metal bellows tends: to increase the minimumdifferential. Also, because it is usually required that the switch bemade small, the spring which opposes the expansion of the bellows mustbe made rather short and, therefore, have a very high rate. 'This highratev also tends to considerably increase the minimum differential.

It is an object of my invention to provide a relatively small switchactuated by gas pressure which switch has a small differential and has arelatively high current carrying capacity.

It is another object of my invention to provide a control having meansto counteract in whole or in part the tendency of the bellows and thesprings to increase the differential of the control.

It is also an object to provide a control means with an additional meansfor reducing the minimum differential of'the switch.

It is a further object of my invention to provide a single means forsnufling out the are at two sets of contacts in a switch.

It is still another object of my invention to provide .a refrigeratorcontrol switch having an improved structure and an improved mechanismpanying drawings, wherein a preferred form of the present invention isclearly shown.

In the drawings:

Fig. 1 is a view partly in section of one form of a refrigerator controlswitch embodying my invention;

Fig. 2 is a section taken along the line 22 of Fig. 1;

Fig. 3 is a section taken along the line 3-3 of Fig. 1; and 10 Fig. 4 isa chart showing a diagram of forces in terms of the movement of thebellows lever as well as a temperature pressure scale therefor. Briefly,I have shown a switch provided with a bellows, a bellows follower leverand a double toggle snap acting mechanism operatively connecting themain switch contacts with the bellows follower lever. A rather short,stiff main spring opposes the expansion of the bellows and maintains thebellows under compression within the range of movement of the bellowsand bellows follower lever. A set of manually controllable overloadcontacts are also provided and a combined electromagnetic blow-out coiland thermal overload heater are provided for snufilng out the are atboth sets of contacts and for providing the thermal overload of thesolder pot type. The thermal overload is of the trip-free type.

The spring effect of the bellows and the high rate of the main springtend to make the differ-- ential of the switch rather high, for example,about 13 F. This is satisfactory for household refrigerating systemswhere the bellows is operated according to evaporator temperature.However, if the switch is to be controlled by air temperature, thistemperature differential must be reduced. In order to reduce thistemperature differential, I connect a tension spring to the bellowsfollower lever which extends diagonally slightly below the pivot pointof the main lever so that it exerts its greatest force when the bellowsis collapsed and a constantly decreasing force as the bellows expands.'I'his, therefore, has the effect of a spring with a negative rate andoperates to reduce the positive rate of the main spring and the springefiect of the bellows. As shown in Fig. 4, this bellows cancel spring orextra toggle type spring can be so set that it is substantially equaland opposite to the inherent spring of the bellows,-but if desired, thisangularity and characteristic of its spring may be changed so as to havea greater effect sufficient to reduce the effect of the high rate of the.main spring. Through this means the temperature differential of theswitch may be reduced'without changing its size or the limits ofmovement of the bellows and bellows follower lever.

Referring now to the drawings and more particularly to Fig. 1, there isshown one form of refrigerator control switch embodying my invention.This switch is provided with a case 28 of a molded insulating materialsuch as hard rubber or a phenolic condensation product. This case isprovided with a slot 22 which receives the neck of a metal bellows 24.This neck is lodged within the slot 22 of the casing and fastened by athin nut 28. The interior of the bellows 24 is connected by tubing 28 tothe interior of a volatile liquid charged thermostat bulb not shown. Ayoke 38 has an aperture which surrounds the neck of the bellows 24 andhas a tongue 32 which is turned down in the slot 22 which receives theneck of the bellows. One side of the yoke 38, designated by thereference char acter 34, receives a pivot pin 38 to which" is connectedone end of the bellows follower lever 38.

The upper end of the other side of the yoke 38 is notched as indicatedby the reference character 48 so that it may be received by the sides ofan opening 42 provided in the bellows follower lever 38. This aperture42 is elongated in the direction transverse to the notched portion 48 sothat the notched portion 48 may pass through the aperture 42 when thebellows follower lever 38 is in aposition transverse to its properposition. This, therefore, acts somewhat similarly .to a bayonet slotarrangement. The notched lower 38 and thereby limit the expansion of thebellows 24.

The free end of the bellows follower lever is provided with a pair ofnotches 44 which receive the chisel-shaped ends of a secondary snapacting lever 46. The secondary lever 48 is generally U-shaped and on itsopposite end is provided with a slot which receives a T'-shaped member41 having an aperture therein which receives one end of the tension coilspring 48. The opposite end of this tension coil spring is hooked over aturned up car 58 provided upon an L- shaped contact carrying lever 52which is pivoted upon a pivot pin 54 which in turn is supported by abracket fastened to and extending from the adjacent wall of the switchcase 28. This contact lever 52 is provided with portions on either sideof the secondary lever 48 which serve as stops to limit the movement ofthe secondary lever 48.

Part of the contact lever is formed of heavy sheet brass while a secondpart 58 which is riveted to the brass part is made up of a stiff moldedinsulating material which preferably contains fabric. The switchcontacts 58 are located at the end of. the portion 58 and are riveted toH clip 88 which extends around the lower end of the portion 58 and has atongue extending into an aperture provided in the portion 58 to retainthe clip 88. The differential of the snap acting mechanism is determinedby the angularity of the contact lever 52 in open and closed position.The angularity of the contact carrying lever 5.2 is limited by the fixedcontact which is carried by the contact post 82 while the open positionof the contact carrying lever 52 is limited by a differential screw 84which is held within a threaded aperture in the casing and has a pinextending into contact with a portion of the contact carrying lever 52to limit the opening movement of this lever. v

In order to place the bellows 24 under compression and in order tobalance the gas pressure within the bellows, I provide a tension coilspring 88 which is connected at one end to the bellows follower lever 38and its other end to a U-shaped nut I8 which is threaded upon anadjusting screw 12 rotatably mounted at both ends within opposite wallsof the casing 28. The one end portion of this screw extends through thecasing and is provided on the outside with a temperature regulating knobI4. This tempera- I ture regulating knob 14 may be turned to increase ordecrease the tension upon the spring 88 and so will increase or decreasethe gas pressure required within the bellows 24 to move the switchcontacts to open and closed position.

This switch mechanism is also provided with a toggle snap acting singlecycle loading device. This includes a finger manipulator I8 which ispivoted to the case 28 upon a pivot pin I8. This finger manipulator isprovided with a notch 88 which receives a chisel-shaped end of a link 82which has its other end received and slidable within a pair of aperturesprovided in a bracket 84 fastened to the case 28. This bracket isprovided with a rounded protrusion against which rests the springretainer of a small compression type coil spring 88 which is threadedupon a screw 88 having one reduced end portion passing through anaperture in the bracket 84 while the other end portion is provided witha nut 88 and a kerf on the end of the screw.

The link 82 is provided with a slot which receives the spring, the nutand the screw. The

kerf end of the screw engages the end of the slot to hold and to preventthe rotation of the screw. A link 92 is connected to a portion of thelink 82 and extends downwardly therefrom. This downwardly extending link82 has a shoulder and a narrow tongue extending downwardly through anaperture in the bellows follower lever 38. When the finger manipulatorI8 is turned in a clockwise direction about its pivot 18, the link 82 ismoved downwardly so that its shoulder comes into engagement with theflat portion of the bellows follower lever 38 and at the same time thelink 82 is pushed across the center line between the pivot pin I8 andthe hump on the bracket 84 so that the spring 88 will tend to place anadditional force by the throwing of the toggle linkage and the link 82upon the bellows follower lever. This places an additional load upon thebellows 24 and requires a higher pressure and temperature before theswitch may be moved to closed circuit position. When this higherpressure and temperature is attained, the bellows follower lever 38through the link 82 will push the link 82 across its dead centerposition to the position shown in Fig. 1 where it is inactive. This isemployed in household refrigerators to provide a manually initiatedautomatically reset defrosting cycle for the purpose of providing acycle which will remove any frost which may collect on the evaporator.

I have also provided a manual on and off snap acting switch which isactuated by the finger manipulator I82 pivoted upon the pin I84 embeddedin the casing 28. This finger manipulator I82 has a metal extension I88which holds one end of the compression toggle spring I88 provided-withpointed spring retainers at each end,

one of which engages one arm of a contact car-- rying lever IIO pivotedto the casing upon a pivot pin I I2. The other arm of this lever H0has'an extension II4 of an insulating material containing fabric andhard rubber or a phenolic condensation product. The extreme end of thisportion H4 is provided with a clip H6 having a tongue engaging anaperture in the portion II4 for retaining the clip. This clip surroundsthe lower end of the member H4 and is provided with a switch contact II8 which is adapted to cooperate with a stationary switch contact I20mounted upon a stud I22 which is riveted to a movable insulating wallsection I24.

This mechanism provides a snap acting manual switch. It is, however,also used as a thermal overload mechanism and. has a means for resettingthe thermal overload mechanism. In order to do this the casing isprovided with a hollow boss i265 extending from the bottom wall in Fig.l which receives the shaft H20 of the ratchet wheel it. This shaft I28is received within a bushing Hi2 threaded into the hollow boss H20 andfastened to the shaft M8 by a low melting solder. Threaded onto thisthreaded bushing 632 is a soft iron core i341 upon which is mounted acoil of wire i230 which with the core serves as an electromagnet as wellas a thermal overload heater for heating the solder which holds theshaft H28 or" the ratchet wheel. This coil I30 is connected by theconductors I30 and I40 in series with the switch contacts 62, 50, H8 andI20. This electromagnet coil is wound tightly with several layers ofwire instead of very loosely as heretofore so that it will not beinfluenced to any great degree by the temperature of the place whereinthe switch is located.

Recently, it has been customary to locate the switch upon the evaporatorof a household refrigerator and under such conditions the tern peratureof the switch may fluctuate considerably. The tight winding preventsthis fluctuation of temperature from materially varying the operation ofthe thermal overload. In addition, this electromagnet sets up a magneticfield which embraces both sets of switch contacts and also furnishes asmall supply of heat which maintains the switch at a temperature abovethe temperature of the atmosphere within the refrigerator so that therewill be little or no condensation of moisture or deposit of frost uponthe parts of the switch.

The ratchet wheel I30 holds a spring tongue I42 between a pair of teeth.This spring tongue is also fastened to a slidable plate I44 which slideswith the arms I 46 and I48 of a U-shaped bracket which is fastened tothe bottom wall of the case 20. This slide plate also has a hooked endportion I50 which is adapted to engage a portion of the arm I I4 whenthe slide I44 is released by the ratchet wheel. When this projection I50engages the arm II4, it pivots the arm II4 as well as the arm IIO abouttheir pivot II 2 to open the contacts II 8 and I20. At the same time itthrows the toggle spring I08 across its dead center position so that thefinger manipulator I02 is moved to its off position.

The slide plate I44 is provided with an arm I 54 which is pivoted by thepin I56 to the slide plate. This arm has a curved end portion with anotch that is adapted to be engaged by a depending tongue I58 extendingfrom the metal arm I06 attached to the finger manipulator I02. The armI54 is pulled to the left as shown in Fig. l by a tension coil springI62 connected at the other end to the arm I48 while a second spring I84connects the arm I54 to a remote portion of the arm I48. Thus, when theratchet wheel I30 releases the slide plate, the slide plate I44 and thearm I54 move to the left in Fig. 1 under the motive power of the springI62 which is thereby reduced in tension while the spring I64 has itstension increased and thereby raises the arm E54 sufliciently so that itwill be engaged by the arm I58 upon the finger manipulator I02.

Thus, when the finger manipulator I02 is moved from off to "on position,in this circumstance, the arm I58 will engage the notched end of the armI 5 3. This will move the arm I54 and the slidable plate 944 to theright as located in Fig. l and at the same time will cause a portion ofthe face of the arm l5fi to be held against the side of the adjacentportion of the contact carrying lever 52 so that the contacts 50 will beheld in the open position while the contacts H0 and H0 are being closedand the spring tongue M2 is moved into engagement with the ratchetwheel. During this time the finger manipulator throws the toggle springi 00 across the dead center position to move the overload contacts intoclosed position. The contacts 50, however, will remain in the openposition until the finger manipulator is released, at which time the armlt l will also be released by the arm 950 of the finger manipulator 002so that it will be impossible to hold the contacts closed by the use ofthe finger manipulator i 02.

This will prevent the refrigerating system from being forcibly operatedunder overload conditions when the ratchet wheel has released the slideplate I44.

In Fig. 4 I have provided a chart or graph in which. the movement of thebellows follower lever at the bellows point is plotted along thehorizontal scale and the effective pressure in pounds at the bellowspoint is plotted in the vertical direction. The bellows may be assumedas havingan effective area of about one square inch so that thisvertical scale will also represent the gas pressure within the bellows24. Under ordinary circumstances the main spring 08 and the diifenentialscrew 64 are set so that the switch will be closed when the bellows iscompressed and the bellows follower lever is moved upwardly, withreference to Fig. 1, from its extreme lower position a distance of .046inch. The switch will open when the bellows and bellows follower levermove downwardly about .025 of an inch to a position of .021 inch.

In Fig. 4, the line marked Bellows indicates the inherent spring forceof the bellows which is plotted as being negative pressure since ittends to push the bellows follower lever 38 downwardly. The two linesmarked Toggle indicate the force of the toggle spring during themovement of the bellows and bellows follower lever. This force changesfrom positive to negative when the switch cuts on or closes and changesfrom negative to positive when the switch cuts out or opens. Hie forceprovided by the main spring is plotted by the line which is designatedas Main spring with cancel spring. This is a positive force whichincreases with the expansion of the bellows and movement of the bellowsfollower lever. This main spring is required to be strong enough tooppose the force of the bellows plus the force of the gas pressurewithin the bellows plus the force of the toggle spring. However, inorder to do this, the main spring would have to be adjusted to thestrength or pull indicated by the dotted line upon the chart and markedMain spring without cancel spring". As shown in the chart, it wouldrequire about 3.6 lbs. or 3.7 lbs. gas pressure within the bellows toopen the switch.

In the lower left hand corner of the chart in Fig. 4 is a curved linewhich designates the pressure temperature curve of sulphur dioxide,which for the purposes of illustration, is the gas used in the bellowsand thermostat bulb. However, other gases such as methyl or ethylchloride or difluorodichloromethane may be used if desired. Beneath thiscurved line is a temperature scale. The point 3.6 or 3.7 upon thepressure temperature curve of sulphur dioxide represents upon thetemperature scale about 23 F. When the switch moves to cut-on position,the main spring is stretched further and then has an effective pull of12 lbs. Under ordinary circumstances, this plus the force of the togglespring must be balanced by the force of the bellows plus the gaspressurewithin the bellows, in order to make the switch close. However,the force of the bellows decreases as shown by the chart so that agreatly increased gas pressure of lbs. is required to close the switch.This corresponds to a temperature of about 36 F. or 37 F. which makes aswitch differential of about 13 or 14F.

The main spring necessarily has a high rate because of the small spaceprovided. In order to provide an effective temperature adjustment by theknob 14, it is diflicult from the practical standpoint to materiallyreduce the rate of the main spring within a switch structure of such asmall size. This switch is about four inches long, two inches wide andone and one-half inches deep. In Figs. 1, 2 and 3, each dimension isdoubled in size. In order to reduce, the differential of the switch, itis, therefore, necessary to find some means for reducing the rate ofeither the bellows, the main spring or both. However, it is not possibleto conveniently reduce the rate of the main spring or of the bellows.

I, however, have found a way to obtain the same effect. I do this byproviding a tension spring I10 which extends into a slot I12 provided inthe bellows follower lever 30 and is hooked to an aperture located atthe closed end of the slot. The other end of this tension coil spring ishooked in the eye of a threaded pin I14 which is threaded within a nutI16 mounted upon the opposite side of an L-shaped bracket I18 which inturn is riveted to a projection of the arm 34. It should be noted thatthe center line of this spring extends above the pivot point of the mainlever 38 and the spring extends from the main lever 38 at a slight anglethereto. Thus, when the bellows 24 are collapsed tothe cut-oft position,the spring 110 exerts its maximum force aiding the main spring 60. Atthis time, the bellows 24 also exerts its maximum inherent spring force.As the I bellows expands, the inherent spring force of the I bellowsweakens, as shown in the chart, while at the same time the spring I10provides an effective force substantially equal and opposite theinherent spring force of the bellows.

In Fig. l I have located the screw I14 and made a spring I10 of such arate so that it is substantially equal and opposite to the inherentspring force of the bellows through its range of movement between thecut-off and cut-on points. In fact, it is substantially equal andopposite throughout the movement of the bellows. I, therefore, call thisspring a bellows cancel spring because it cancels in effect the inherentspring force of the bellows. By adding this bellows cancel spring, it ispossible to reduce the force of the main spring. It will be seen thatwhen n cancel spring is used, it is necessary to provide a main springwhich has eight pounds of force at the cut-off point and twelve poundsforce at the cut-on point. By employing the bellows cancel spring I10 itis possible to reduce the force of the main spring 68 at the cut-offpoint to 4.6 lbs. while this same spring would have a force of onlyabout 8.6 lbs. at the cut-on point.

The force of the bellows plus the force of the gas pressure must besuiiicient to equal the force of the toggle plus the force of thebellows cancel spring, plus the force of the main spring when a. cancelspring is used. When no cancel spring is used, the bellows force plusthe gas pressure must equal the force of the toggle plus the mainspring. However, since the bellows cancel spring has a negative rate;that is, its force is reduced as the bellows expands, it reduces theforce normally required of the bellows and gas pressure to move theswitch to cut-on position by the amount that the force of the bellowscancel spring is reduced. Since the bellows cancel spring has reducedthe force about 1.2 or 1.3 lbs., a lesser gas pressure is required.Thus, the chart shows that at the cut-on point, the gas pressurerequired when a cancel spring is used is about 8.8 lbs. This correspondsto about 33 F. so that the differential of the switch by the use of thiscancel spring has been reduced 3. v

However, since the main spring need not supply so great an amount offorce, its rate may also be reduced slightly if desired. Furthermore,the bellows cancel spring may be located at other angles and may have a.greater force so that it would provide a more variable negative rate soas to not only cancel the inherent spring force of the bellow but alsoto cancel a portion of the force of the main spring so that in effect itwould reduce the rate of the main spring. Thus, by employing thisbellows cancel spring, I am able to considerably lower the diflferentialof the switch without changing the relationship, sizeand force of any ofthe elements of the switch, but merely by the addition of the bellowscancel spring which may not only be used to cancel out the inherentspring force of the bellows, but also to reduce the effective rate ofthe main spring and thus to considerably reduce the difierential of theswitch.

While'the form of embodiment of the invention as herein disclosed,constitutes. a preferred form, it is to be understood that other formsmight be adopted, all coming within the "scope of the claims whichfollow.

What is claimed is as follows;

1. A control means including a pressure operated diaphragm means havingan inherent natural resilient resistance to movement from a neutralposition, a means to be operated by said diaphragm means, and cancellingmeans providing a force substantially equal and opposite to saidinherent natural resilient resistance of diaphragm means, and springmeans providing a force substantially equal and oppositeto said inherentnatural resilient resistance of the diaphragm means for substantiallycancelling said resilient resistance. I

3. A control means including a pressure op- 2,1s9,ees

erated diaphragm means having an inherent natural resilient resistanceto movement from a neutral position, a means to be operated by saiddiaphragm means, and resilient over-center means providing a forcesubstantially equal and opposite to said inherent natural resilient resistance of the diaphragm means for substantially cancelling saidresilient resistance.

4. A control means including a pressure operated diaphragm means havingan inherent natural resilient resistance to movement from a neutralposition, a means to be operated by said diaphragm means, a snap actingmeans connecting said means to be operated and said diaphragm means, andmeans acting upon said diaphragm means providing a force substantiallyequal and opposite to said inherent natural resistance of said diaphragmmeans for cancelling said natural resistance.

5. A control means including a pressure operated diaphragm means, aswitch means operated by said diaphragm means, means for limiting theexpansion of the diaphragm means, said diaphragm means having aninherent spring force decreasing with expansion of the diaphragm meansin a direction aiding the expansion of the diaphragm means, and a springmeans providing throughout the limited expansion of the diaphragm meansa decreasing positive resistance with the expansion of the diaphragmmeans opposing theexpansion of the diaphragm means.

6. A control means including apressure operated diaphragm means, aswitchmeans operated by said diaphragm means, means for limiting the expansionof the diaphragm means, said diaphragm means having an inherent springforce decreasing with expansion of the diaphragm means in a directionaiding the expansion of the diaphragm means, a yielding means providingan increasing resistance with the expansion of the diaphragm meansopposing the expansion of the diaphragm means, and a yielding meansproviding throughout the limited expansion of the diaphragm means apositive decreasing resistance with the expansion of the diaphragm meansopposing the expansion of the iting the expansion of the diaphragmmeans,

and a yielding means providing throughout the limited movement of thediaphragm means a decreasing positive resistance with the expansion ofthe diaphragm means opposing the expansion of the diaphragm means.

8. A control means including a pressure operated diaphragm means, aswitch means operated by said diaphragm means, means for limiting theexpansion of the diaphragm means, and a yielding spring means providinga decreasing positive resistance to the expansion of the diaphragm meansopposing the expansion of the diaphragm means throughout the limitedexpansion of the diaphragm means.

9. A control means including a pressure operated diaphragm means, aswitch means opened and closed at certain positions of movement of thediaphragm means, and a yielding means providing a decreasing resistancewith the expansion of said diaphragm means from one of said certainpositions to another, said yielding means providing a positiveresistance to the expansion of said diaphragm means between saidpositions.

10. A control means including a set of switch contacts, a diaphragmmeans for operating said contacts, a second set of switch contactslocated adjacent said first set of contacts, and magnetic means locatedbetween said sets of contacts for creating a magnetic field envelopingboth of said sets of contacts.

11. A control means including a set of switch contacts, a diaphragmmeans for operating said contacts, a second set of switch contactslocated adjacent said first set of contacts, and electromagnetic meanslocated between said sets of contacts and energized by electric energyfiowing through one of said sets of contacts for creating a magneticfield enveloping both of said sets of contacts.

e 12. A refrigerator control to be mounted within the compartment to becooled of a refrigerator cabinet, said control including a casingcontaining a diaphragm means, a switch mechanism operated by thediaphragm means, an electric circuit controlled by said switch means,and means for preventing corrosion of the mechanism in said casingincluding an electric heater electrically connected to said electriccircuit and controlled by said switch mechanism for heating therefrigerator control.

ALBERT O. -GROOMS.

